1. Field of the Invention
The present invention relates to a legged moving robot, and more particularly to a system for controlling the amount of electric energy generated by a fuel cell on a legged moving robot.
2. Description of the Related Art
Heretofore, legged moving robots have been powered by an external power supply connected via a power cable or a secondary battery such as lithium-ion battery or the like. However, a legged moving robot that is powered by an external power supply connected thereto via a power cable suffers a serious problem in that the range of movement of the legged moving robot is limited by the power cable.
A legged moving robot that is powered by a secondary battery such as lithium-ion battery or the like carried thereon is free of limitations on the range of movement thereof. However, the energy storage capacity of the secondary battery is limited because of a limited weight which can be borne by the legged moving robot. Conventionally, the energy storage capacity of secondary batteries available for use on legged moving robots has limited the continuous walking time of the legged moving robots to about 30 minutes. Furthermore, the secondary batteries have been disadvantageous in that it takes a relatively long period of time to charge the secondary batteries.
One solution would be to install an engine-operated electric generator on legged moving robots. Since, however, the engine of the electric generator emits harmful exhaust gases and causes vibrations, the engine-operated electric generator is not suitable for use on legged moving robots particularly if they operate in such environments which demand cooperation with human beings.
According to one proposal, a fuel cell which has a greater energy storage capacity per weight than lithium-ion batteries and which neither emits harmful gases nor causes vibrations is installed as a power source on a legged moving robot. The output electric energy from the fuel cell varies depending on the amount of hydrogen supplied as a fuel to the fuel cell.
Hydrogen is generated by a reformer from a fuel such as methanol or the like by way of a chemical reaction. The amount of hydrogen generated by the reformer can be increased by increasing the temperature of a heater of the reformer or increasing both the amount of air supplied to the reformer and the amount of a fossil fuel supplied to the reformer to increase the pressure for thereby accelerating the chemical reaction. For this reason, after the reformer is instructed to increase the amount of hydrogen generated thereby, it takes a certain period of time or time delay before the amount of hydrogen generated by the reformer is actually increased.
When the load on an actuating system including a motor on the legged moving robot is abruptly increased as when the legged moving robot starts walking, the reformer is instructed to increase the amount of hydrogen generated thereby for enabling the fuel cell to generate electric energy large enough to meet the load. However, on account of the above time delay, the amount of hydrogen supplied to the fuel cell does not immediately increase, possibly resulting in a shortage of electric energy supplied from the fuel cell to the actuating system.
In order to eliminate the above time delay, a reservoir tank for storing hydrogen may be connected to a fuel passage extending from the reformer to the fuel cell. The reservoir tank needs to be of a sufficiently large size to be able to supply an amount of fuel to the fuel cell which can meet the abrupt increase in the load as when the legged moving robot starts walking because the legged moving robot consumes largely different amounts of electric energy when it is at rest and when it is walking. The large-size reservoir tank requires a large installation space and is relatively heavy.